review(#1660, #1663): associative sweep scan, arc angles, viewport off bit

- refresh_associative_sweeps runs on every edit and scanned the xdata of
  every entity; it now returns at once when no associative swept surface
  exists (its application is not registered) and looks at surfaces only.
- An arc's end angle was raised by TAU in a loop, which never ends on a
  huge angle from a damaged file; the sweep is taken with rem_euclid.
- The sweep DELOBJ test expected surface sweeps to delete their sources,
  which #1663 changed on purpose: an associative surface keeps them.
- codec c9ffcac (opencadcodec #103) adds an explicit viewport-off bit: the
  viewport on state is read with is_on() and set with turn_on()/turn_off()
  everywhere, so a viewport the file marks off shows off and can be turned
  back on from Properties.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/scene/model/sweep_command_model.rs

@@ -475,8 +475,10 @@ pub fn assoc_edge_curve(entity: &EntityType) -> Option<(i32, codec::objects::Ass
         EntityType::Arc(value) => {
             let normal = glam::DVec3::new(value.normal.x, value.normal.y, value.normal.z).try_normalize()?;
             let axis = arbitrary_x(normal);
-            let mut end = value.end_angle;
-            while end <= value.start_angle { end += std::f64::consts::TAU; }
+            // The end past the start by the arc's sweep; an equal pair is a
+            // full turn. (A loop adding TAU never ends on a huge angle.)
+            let sweep = (value.end_angle - value.start_angle).rem_euclid(std::f64::consts::TAU);
+            let end = value.start_angle + if sweep > 0.0 { sweep } else { std::f64::consts::TAU };
             Some((11, K::Arc, arc(glam::DVec3::new(value.center.x, value.center.y, value.center.z), normal, axis, value.radius, value.start_angle, end)))
         }
         EntityType::LwPolyline(polyline) => {

src/scene/model/sweep_model.rs

@@ -13,7 +13,7 @@ use codec::EntityType;
 
 use crate::entities::curve::entity_curve;
 pub use super::sweep_command_model::{
-    is_sweep_path, is_sweep_profile, scaled_sweep_path_refusal, spatial_profile, spatial_sweep_record, surface_sweep_record, sweep_expressions, link_sweep_expressions, link_sweep_sources, sweep_sources, resweep_from_sources, surface_associativity, set_surface_associativity, assoc_edge_curve, sweep_record, sweep_refusal_code, sweep_selection_options, swept_surface_entity, swept_with_options,
+    is_sweep_path, is_sweep_profile, scaled_sweep_path_refusal, spatial_profile, spatial_sweep_record, surface_sweep_record, sweep_expressions, link_sweep_expressions, link_sweep_sources, sweep_sources, SWEEP_SOURCES_APP, resweep_from_sources, surface_associativity, set_surface_associativity, assoc_edge_curve, sweep_record, sweep_refusal_code, sweep_selection_options, swept_surface_entity, swept_with_options,
 };
 
 /// A drawn profile, as the kernel wants it: the plane it lies in and the